1. Field of the Invention
The present invention relates to a vehicle glass run, which is mounted on a door frame of a vehicle and a method of manufacturing the same. More particularly, the invention relates to a structure of a corner part and a method of manufacturing the same.
The present application is based on Japanese Patent Application No. 2000-251946, which is incorporated herein by reference.
2. Description of the Related Art
A conventional vehicle glass run mounted on the side door (frame) is disclosed in Unexamined Japanese Patent Publication No. Hei. 10-44786. The vehicle glass run is provided with extrusion parts for the roof and pillars, and the corner molding parts connecting those extrusion parts together. The extrusion parts and the corner molding parts are U-shaped in cross section. A door glass is slidably moved within and along the sliding grooves of the glass run. Sealing lips contact to the surfaces of the door glass, which are sealing between the inside and outside of the vehicle. Further, the sealing lips guide an upward and downward slide movement of the door glass.
The vehicle glass run is manufactured by the following process. Thermoplastic elastomer is extruded and cut to have a predetermined length to form extruded pieces. The extruded pieces are set in a mold. And, thermoplastic elastomer is injected into a cavity. The injected thermoplastic elastomer welds the surfaces of the terminal ends of the extruded pieces by heat and pressure, thereby connecting them. The thermoplastic elastomer is cooled and solidified. As a result, the corner molding parts connecting the terminal ends of the extruded pieces in an L shape are formed. The corner molding parts are shaped resembling the corners of the side door.
In the vehicle glass run, a reliable sliding movement of the door glass is folded with the side ends of the pillar-side extrusion parts. Accordingly, the U-shaped sliding groove must be deep. The merely supports the upper-side end of the door glass put thereinto. Attempt is made to design the roof-side extrusion part with a shallow groove to make the external appearance good. When the vehicle glass run is designed such that the grooves of the pillar-side and roof-side extrusion parts are different in depth, viz., the cross sectional shapes of them are different, and both the extrusion parts are connected by the corner molding parts which are various in cross sectional shape, the size of the pillar-side portion of the corner molding part is larger than the roof-side portion of the corner molding part.
Enlargement of the corner molding part implies that a distance from the gate position for injecting the thermoplastic elastomer to the terminal end of the extrusion part is increased. Accordingly, the thermoplastic elastomer cannot rapidly travel and reach the terminal ends of the extrusion parts, while keeping its high temperature. As a result, the thermoplastic elastomer cannot weld and connect the terminal ends of them by heat and pressure. If the heat welding of them is insufficient, a connecting strength at the connecting part between the extrusion part and the corner molding part decreases. As a result, there is a danger that both the parts are separated from each other with the sliding movement of the door glass.
Accordingly, an object of the present invention is to provide a vehicle glass run and a method of manufacturing the same in which corner molding parts are connected at high connecting strength to extrusion parts, and those are firmly supported on a frame.
According to one aspect of the invention, there is provided a vehicle glass run which is to be mounted on a frame having a substantially linear frame body and L-shaped frame corner parts, connected to the frame body, and is made of a thermoplastic elastomer and slidably supports a door glass. The vehicle glass run comprises: a horizontal-side extrusion part and vertical-side extrusion parts, which are mounted on the frame body; and corner molding parts, mounted on the frame corner parts, for connecting together the terminal ends of the horizontal-side extrusion part and the vertical-side extrusion parts by injection molding; wherein the horizontal-side extrusion part and the vertical-side extrusion parts are made of a first material of an olefin thermoplastic elastomer, and the corner molding parts are made of a second material which is an olefin thermoplastic elastomer and has a viscosity lower than that of the first material.
In the vehicle glass run thus constructed, the first material of an olefin thermoplastic elastomer is extruded to form the horizontal-side extrusion part and the vertical-side extrusion part. Those parts are both connected together by heat welding using the corner molding parts formed by injecting the second material.
In the injection molding, the second material is injected in a molten state, and reaches the terminal ends of the horizontal-side extrusion part and the vertical-side extrusion parts and melts the surfaces of the terminal ends of them by heat and pressure. Those terminal ends are easily connected together since the olefin thermoplastic elastomer that is the same as the first material is used.
Further, the viscosity of the second material is lower than that of the first material. And its fluidity is large. Therefore, even if a distance from the injection position to the terminal ends of the horizontal-side extrusion part and the vertical-side extrusion parts is long, the material swiftly reaches the terminal ends while keeping its high temperature and molten state. It melts both the terminal ends of them by heat and pressure and firmly heat-welds to them. Therefore, even when the cross sectional shape of the horizontal-side extrusion part is different from that of the vertical-side extrusion part, and the corner molding parts are greatly different in length, the corner molding part reliably heat-welds to both the terminal ends. The resultant product has a high connecting strength.
If the second material of low viscosity is used for the corner molding parts, a hardness of it is slightly increased. However, it little affects the use performance of the vehicle glass run. Since the first material as the normal material is used for the vertical-side extrusion parts and the horizontal-side extrusion part, there is no chance that the use performance of the vehicle glass run is degraded.
In the vehicle glass run, a melt flow rate (referred to as MFR) of the materials are measured by K7210 (corresponding to ISO 11339) testing method prescribed in JIS (Japanese Industrial Standard), and MFR of the first material is 45 to 70 g/10 min. and MFR of the second material is 70 to 100 g/10 min. The reason why MFR of the second material is 70 to 100 g/10 min follows. If it is smaller than 70 g/10 min, its fluidity is small. Before it reaches the terminal ends of the horizontal-side extrusion part and the vertical-side extrusion parts, its temperature drops. And, its heat welding to the terminal ends is insufficient, and the connecting strength is also unsatisfactory. If it exceeds 100 g/10 min, its fluidity is excessively large. Burrs will be formed and the material will leak (sag and run) to the horizontal-side extrusion part and the vertical-side extrusion part. Accordingly, an additional step to remove the burrs is essential to complicate the molding process.
Also in the vehicle glass run, the first material may mainly contain 70 weight parts of ethylene-polypropylene rubber (EPDM) and 30 weight parts of polypropylene (PP). The second material may be prepared by adding a third material whose viscosity is lower than that of PP of the first material, to the same kind of material as of the first material as a main material.
In the vehicle glass run, parts of the horizontal-side extrusion part by which a door glass are supported are smaller than those of the vertical-side extrusion parts, and each the corner molding part includes a variable connecting part whose cross section gradually decreases in area toward the horizontal-side extrusion part, from the vertical-side extrusion part. The vehicle glass run thus constructed is well adaptable for a case where the corner molding part is likely to be long.
According to another aspect of the invention, there is provided a method of manufacturing the above vehicle glass run, comprising: extruding the first material of an olefin thermoplastic elastomer to form an extruded piece for the vertical-side extrusion parts and the horizontal-side extrusion part; setting the extruded piece so as to form a cavity in a mold; and forming the corner molding parts connected to the extruded piece by injecting the second material whose viscosity is lower than that of the first material into the cavity of the mold.
The vehicle glass run of the invention may preferably be manufactured by the manufacturing method mentioned above.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.